Stepwise thermal analysis technique for estimating mercury phases in soils and sediments

Azzaria, L. M.; Aftabi, Alijan

doi:10.1007/bf00342272

Cited by 31 publications

(18 citation statements)

References 8 publications

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“…Hg concentrations higher than those generally encountered in natural environments were used in this study to determine the reaction mechanisms and to demonstrate saturation of the binding sites. However, higher Hg concentrations, up to 500 nM, can be observed in contaminated environments (14,45,52,53). At these sites, Hg(0) is present due to its prior industrial use and/or production.…”

Section: Resultsmentioning

confidence: 99%

Mercury reduction and complexation by natural organic matter in anoxic environments

Bian

Miller

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

299

272

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Mercuric Hg(II) species form complexes with natural dissolved organic matter (DOM) such as humic acid (HA), and this binding is known to affect the chemical and biological transformation and cycling of mercury in aquatic environments. Dissolved elemental mercury, Hg(0), is also widely observed in sediments and water. However, reactions between Hg(0) and DOM have rarely been studied in anoxic environments. Here, under anoxic dark conditions we show strong interactions between reduced HA and Hg(0) through thiolate ligand-induced oxidative complexation with an estimated binding capacity of ∼3.5 μmol Hg/g HA and a partitioning coefficient >10 6 mL/g. We further demonstrate that Hg(II) can be effectively reduced to Hg(0) in the presence of as little as 0.2 mg/L reduced HA, whereas production of Hg (0) is inhibited by complexation as HA concentration increases. This dual role played by DOM in the reduction and complexation of mercury is likely widespread in anoxic sediments and water and can be expected to significantly influence the mercury species transformations and biological uptake that leads to the formation of toxic methylmercury.Hg-dissolved organic matter complex | environmental factors | methylation | redox M ercury (Hg) is well known to bioaccumulate and biomagnify as neurotoxic methylmercury (CH 3 Hg + ) in organisms, particularly fish (1-3). Biologically mediated production of CH 3 Hg + predominantly occurs under anaerobic conditions (4-8). However, the environmental factors that determine Hg availability to methylating bacteria and its transformation under these conditions remain poorly understood (1, 9-12). In particular, the coupled reactions between Hg redox transformation and complexation with natural dissolved organic matter (DOM) remain unclear, yet this process may critically control the speciation, biological uptake, and methylation of aqueous Hg in aquatic environments (9)(10)(11)(13)(14)(15)(16)(17). DOM occurs in all natural sediments and water, usually at concentrations much higher than Hg (1, 9). It is known to form exceptionally strong complexes with the oxidized mercuric species, Hg(II), due to its coordination with reduced sulfur (−S) or thiol (−SH) functional groups in DOM at relatively high DOM:Hg(II) ratios (11,(18)(19)(20)(21). Such complexation has been shown to limit Hg(II) availability for bacterial methylation (9, 22, 23); however, facilitated uptake and methylation are also reported, especially when Hg(II) is complexed with small molecular-weight thiol compounds such as cysteine (5,24).Although a large body of literature is now available on the interactions of oxidized Hg(II) species with DOM, reactions between reduced gaseous Hg(0) and DOM have rarely been examined in natural sediments and water where dissolved Hg(0) is also observed (16,17,(25)(26)(27)(28)(29)(30)(31). Hg(0) has a solubility of ∼56 μg/L in water (32). Its formation can be mediated biologically (25, 26, 33), chemically (34, 35), or photochemically in the aquatic environment (15-17, 27-31). However, the role pla...

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Section: Resultsmentioning

confidence: 99%

Mercury reduction and complexation by natural organic matter in anoxic environments

Bian

Miller

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

299

272

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“…Other methods, such Ž as sequential chemical extractions Revis et al, . 1989;Sakamoto et al, 1992 and thermal desorp-Ž tion Azzaria and Aftabi, 1991;Biester and Scholz, . 1997 , have been used to indirectly determine the speciation of mercury by measuring extractable fractions of mercury and equating them to unique mercury species.…”

Section: Introductionmentioning

confidence: 99%

Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy

Kim

Brown

Rytuba

2000

The Science of the Total Environment

183

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“…A good correlation of Hg with S, Zn, Cu, Pb, Environ Earth Sci Tl, Se, As and Fe reflects its inorganic association, possibly in pyrite and sphalerite. However, Swaine (1990) and Azzaria and Aftabi (1991) reported organically bounded forms of Hg in soils, sediments and rocks. There are no precise, restrictive, allowable values for Hg in coal combustion and coal mining, but it is certain that mercury is a highly neurotoxic volatile element and about 1.7 kg/day of Hg is released by coal combustion to the atmosphere (Brookins 1990), soil and groundwaters.…”

Section: Mercurymentioning

confidence: 95%

Geochemical and environmental baseline of major and trace elements in Zarand coals, southeastern Iran

Aftabi

Shojaei

Nezhad³

2014

Environ Earth Sci

Self Cite

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In order to establish a geochemical baseline for environmental impacts of coal measures in Rhaeto-Jurassic Zarand coalfields, multielement geochemistry of 22 host rocks, 26 coal seams and 9 coal ashes was determined by ICP-MS, ICP-AES, XRF, PGM-ICP24 and CV-ASS methods at ALS Chemex, Canada. The discrimination diagrams of major trace elements show a continental margin granitoid arc provenance for coal-bearing sandstones and shales. Compared to the crustal abundance, world coals and American coals, the geochemical baseline for most of the elements is within the limits of safeguard background values. However, higher contents of Li (49.31-185 mg/kg), Rb (71.12-131.73 mg/kg), Cs (7.13-16.12 mg/kg), V (72.19-213.1 mg/kg), Th (7.63-11.8 mg/kg), As (10.1-31.31 mg/ kg), Nb (5.4-15.07 mg/kg),Ta (0.4-1 mg/kg), Hf (1.89 mg/ kg), Ga (12.63-32.16 mg/kg), Ce (37.31-64.28 mg/kg), Pb (40.23-55.76 mg/kg), Cr (48.23-133 mg/kg), Zr (60.39 mg/ kg), and Hg (0.24 mg/kg), are of some environmental as well as economic concerns. The low values of B (0.12-12 mg/kg), S (7,839-10,567 mg/kg) and Zn (63.25-157.6 mg/kg) in Zarand coals may indicate a fluvial freshwater environment of coal deposition. Au, Pt and Pd contents are slightly higher than the crustal abundance and further studies are required for their possible environmental and economic evaluation. As the mean Hg value in ash (0.0075 mg/kg) is almost 32 times lower than the mercury content of the coal seams (0.24 mg/ kg), it is noteworthy that much of Hg is released by coal combustion to the atmosphere, which has certainly a detrimental environmental impact. The Ce, Cs, Ga, La, Li, Rb and V values are much higher than the average world and American coals and merit further investigations for being the economic by-products.

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Stepwise thermal analysis technique for estimating mercury phases in soils and sediments

Cited by 31 publications

References 8 publications

Mercury reduction and complexation by natural organic matter in anoxic environments

Mercury reduction and complexation by natural organic matter in anoxic environments

Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy

Geochemical and environmental baseline of major and trace elements in Zarand coals, southeastern Iran

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